Extrusion control system



United States Patent 3,184,788 EXTRUSION CONTRQL SYSTEM Edwin A. Serrano, 1633 W. Cubbon St., Santa Ana, Calif. Filed Feb. 5, 1963, Ser. No. 256,460 7 Claims. (Cl. 18-2) Broadly this invention relates to an extrusion control system. More specically the invention is concerned with an electrical control system for automatically adjusting a puller motor associated with an extrusion process to maintain the dimensional size of the article extruded by the process to within close tolerance of a desired size.

One of the major problems encountered in conjunction with high volume extrusion processes, especially in the plastics art, is the problem of maintaining the dimensions of the articles formed by the process Without the necessity of sacrificing production volume or the quality of the extruded article. When continuous lengths of extruded plastic pipe, rods or beams are being formed it is the customary procedure to utilize an extrusion head through which fluid plastic is forced and a motor operated puller mechanism to apply a pulling force on the extruded article. This pulling force serves to extend the extrusion articles until they are chemically set to a required degree of rigidity and to increase the speed of the plastic material through the extrusion head. Due to the initial ilow characteristics of the plastic material this pulling force frequently tends to overly stretch the articles or cause them to increase in diameter. When this occurs it is required that an operator adjust the speed of the pulling motor to permit the extruded article to assume its correct dimension. This type of control is objectionable because of the diiiiculty encountered by the operator to anticipate ilow characteristics of the plastic material due to its rapid change from a iiuid to a solid.

In consideration of the problems set forth above it is quite obvious to one skilled in the art that a system capable of automatically providing effective adjustment of the puller head, such as is provided by this invention, would constitute a major improvement in the art.

Accordingly, it is an object of the present invention to provide a control system having automatic operation which is capable of overcoming the disadvantages enumerated above.

Another object of the present invention is to provide a control system which responds to a particular characteristic of an extruded article to impose automatic control of the characteristic.

A further object of this invention is the provision of a control system responsive to a dimension of an extruded article to effect automatic control of the dimension.

It is a more specific object of the present invention to provide an electrical system utilized in conjunction with an extrusion process comprising an extrusion head and a puller motor wherein the control system senses a dimension of an article being produced by the process to regulate the speed of the puller motor to control the dimension of the article to within desired limits.

It is still another object of this invention to provide a control system for regulating an extrusion process which is inexpensive of manufacture, dependable in op eration,readily removed and installed in operating position and one c apable of performing properly through long periodsof operation.

The manner in which the advantages of the present invention are more particularly realized and its further objects and features achieved will become more clearly apparent from the subsequent detailed description of the ldj Patented May 25, 1955 ICC invention taken with reference to the accompanying drawings in which:

FIG. 1 is a vschematic representation of a preferred form of the invention showing detector and motor conA trol units associated with extrusion equipment; and

FlG. 2 is a schematic representation of a control circuit utilized in conjunction with the arrangement in FIG. l.

The accompanying drawing is primarily intended so as to illustrate a presently preferred means of constructing a control system falling within the scope of this disclosure. lt is to be understood that those skilled in the art to which the invention pertains may eiect altera- `tions in the embodiment of the system disclosed by the use of routine and ordinary engineering skills without departure from the inventive concepts of the system. Also, further equivalent means can be employed in order to accomplish the operations and structural advantages of the invention.

As an aid toward understanding this invention it can be stated in essentially summary form that the preferred embodiment to be described involves a mechanically movable switch operating feeler that is biased to have one end in sliding contact with the outer wall of an extruded tube at a point along the length of the tube a short distance from where it emerges from an extrusion head. The feeler is arranged in a manner whereby an opposite end of the feeler will move a plurality of switching contacts in accordance with changes in the diameter of the extruded tube. These switching contacts are arranged to operate control circuits that regulate the speed of a puller motor arranged to apply a pulling force to the extruded tube proportional to the speed of the motor. Since the diameter of the extruded tube will decrease with increased motor speed and increase with decreased motor speed two control circuits are providedone for increasing and the other for decreasing motor speed. The switch contacts are arranged such that neither of these control circuits will be energized as long as the sensing end of the feeler remains within a certain range of movement represented by a range of tolerable variation in the diameter ofthe nished tubing. The switching contacts also control other circuits arranged to actuate an indicating system providing a visual representation of the functional state of the control system.

The invention can be more fully understood by referring to the accompanying drawings in which FIGS. A1 and 2 are schematic representations of the control circuit and its relationship to the conventional plastic extrusion head 10 and puller assembly 12 which are required to produce the extruded tubing 14 shown extending between the extrusion head 10 and the puller assembly 12. As may be s een in FIG. l, the detector unit 16 having a suitable housing 18 is represented as being disposed adjacent the tubing 14 so that a feeler probe 20 is positioned with its sensing end opposite a point 22. of the tubing between the `extrusion head 1i) and the puller assembly 12.

of the rod With respect tothe guide sleeve 32. The Y other end 34 of the rod which extends into the housing 18 is attached in fixed relation to a common switch support' bar 36 which is in turn secured in a conventional manner to movable Contact springs 38, 40 and 42 of a conventional multiple circuit leaf spring switch d. T his switch fur-ther includes outer leaf springs 46 and 43 and inner leafsprings 50 and 52. Single contacts Sl,l

56, S, 6l), 62 and 64 are provided onleaf springs 46, 38, Sil, 52, 42 and 4S, respectively. The movable Vleaf spring 40 is provided with a double Contact 66 which f-is independently engageable with either of the contacts Y the probe -upwardly as viewed in FIG. l a sufficient distance :to close contacts 66 and 58 thereby energizing a circuit including the leads 68 and 'itl connected to the leaf springs 4t) and 56, respectively. Further increase lin the diameter to .008 of an inch and in excess thereof will cause the contacts 56 and 5410 close to energize a circuit including the leads 72 and 74 respectively connected to the leaf springs 46 and 3S. Similarly, reverse movement of the probe from its normal position causes contacts 66 and 60 to close and continued movement ot.

the probe causes contacts 62 and 64 to close thereby energizing the circuits associated with leads 68, 7S and 82, 82 connected to lead springsdt), 52 and 42, 48, respectively.

The leads 63, 70, 72 and 7S are connected a-t their other ends to the plug terminals D, C, B and A of the male half 34 of a conventional Jones plug S6 which plugs cooperate with the plug receiving sockets D', C', B', and A', respectively, of the female half SS of the Jones plug shown in FIG.V 2. lt is :to be noted that the plug terminals E and F of the plug half 84 are connected by leads V8S and 9610 the terminals of a speed increasing `sole-` noid operated switch 92 of a conventional speed control unit g4 used for controlling the pulling speed of the puller assembly 12. Similarly, terminals G and H are connected by leads 96 and 98 to a speed decreasing switch 1li@ of the speed control unit.

These speed control switches are connected in a conventional fashion to a reversible rheostat motor 162 as represented by the dashed lines 1514 and 106. The motor 102 is utilized to drive a contact arm 19S in a speed increasing or decreasing :direction along a resistance element 116- as commanded by the switches 92 and 160.

VSuch movement `of the contact arm regulates the magnitude of currentliowing from the puller drive motor. supply :terminal 112 throughlead 114, con-trol arm 168,"

the adjusted length of the resistancellltl, lead 116, the

lield winding 118 of the puller assembly drive motorl andlead 126 to the other supply terminal 122; v The aboveV described switching arrangement afforded by the switch '44 and the connections through the lones plug S6 .areutilized in conjunction with the control: cir- 13d, 136,138,141@ and 142;,a locking relay 14d; thermal time delay switch 146; filament transformer"1418;V and Ia -low voltage transformer 151i. y Power is supplied to thejcontrol circuits ,through a V"plug 152 adapted tobe connectedto a-conventionalll7 Y volt powersource. The power leads 154 and 156 connect .to the plug'152 through-an on-otf switclr andL protective ruses 160 and i162 ytothe power leads 16d and;166.p Leads 164 and 166 are Vconnected acrossithe Y primaryfwinding168 .of the ilarnent transformer 148vr by connecting leads 176 and 172, 171i, The primary winding 176 01' the low voltage `transformer 159 is providedV 4 with power through leads 178, 180, and 136.

The power lead 166 is further connected by leads 188, 1% and 192 to one side of variable input resistances 194', 196 and 128 of tetrodes 126, 12S land 130; and to the junctions ofrresistors 200, 202 and 264, and plate circuit capacitors 2116, 208 and l210 of tetrodes 126, 128 and 130, respectively by the leads 212; 192, 214; and 192,

Power lead 166 is also connected by the-leads 190 and 218 to one side of the ilarnentl ofthe indicator lamp 220 whose other side is connected by the lead 222 to the contact 224 ofthe normally open contacts 224 and 226 of the lockingrelay 144. The other contact Y226 is conniected by the lead 22S and lead 180 to the other power 182 and leads 134 lead 164. The -lead 222 is further connected by a lead 236 and leads 232 and `234 to the cathode VV236 and second grid 238 of the tetrode 130. Thelead V228 yis further connected by lead 241i. to thenormally open contact 242 of the relay 133 whose othernormally open contact 243 is connected by the leads 244, 246, 248k and 250 to the cathode 252 and secondV grid 254 of the tetrode 128. The lead 244 is furtherconneoted by'lead 245 to the normally open contact 256 of the relay 134 whose other normally open contact 258 is connected by the lead 260 to the normally open contact 1262k of relay 132 Whose other normally open contact 264 isconnected by leads 266, 26S and 276 Ito the cathode `272 and second grid 274 of the tetrode 126.

Power lead 166 is further connected through kthe lead 218 by lead 276 to one yside of the filament Vof an indicator lamp 273 the other side of which filament is connected by lead 286 to the normallyeclose'd contact 282 of the locking relay 144 whose other normally" closed Contact 284 is connected by the leads 286, 266 and 268 to the cathode 272 of the tetrode 126. Lead 2S() also connects the power lead 166 to the terminal G of the l ones plug half 124 by the leads 288 and 290 which are connected to the normally open contacts 292 and 294, respectively, of the relay 146; Similarly, lead 230 connects power lead 166 to the terminalE of the Jones plug half 124 fbylea-d 296 Vand 29S which, respectively are connected to the normally open contacts 460 and 462 of the relay-142. The power lead 166 is also connected directly to the terminals F and H of lthe Jones plug halt 12d by leads'304 and 366.

The solenoid coil 368 of the relay 132 is energized by the output ofthe tetrode 128 byfmeans of the output leads 310 and v312. Energzation of the solenoid coils 314 and .316 of the relays 134 and 146, respectively,is eilectedY from the secondary winding4 318 ofthe lojwyoltage transformer 1513 by means of the leads'320, 322 and 324 leading from one side of the transformer and from theother side ot the transformer` 151i through switchcontacts 66 and'66 when l they close as aV result of val decrease'in the diameter of the `connected from ,terminal Dot the Jones plug half 8d and l contact V66.01 switch 44,*the: lead 'iextending between the contact 6tland the Jones plug terminal A, the lead 33d extending between the Jones` plug lterminal A' through normallyclosed contacts '332 and 334-01 relay 136, lead 336 extendingto the other side of .the solenoid winding 314 of relay'134,-and Vthe 'lead 338.extending to the other sideY ,of theV solenoid winding 316 ofthe Yrelay 142.

f Solenoid windinglltl and theloclring solenoid'winding 1 .relay 342,701 the' relay 136ffa'nd the locking relay 144i are energized from.` the power lines 164 and 166.135( theV lead v 178 extending-.toene sideotthge winding dlfand lead 321e Y extendingtrornv lead 173191 one'side ofthe winding 342; v

and by the output ofthe tetrode. V comprising the leads 3416' and lidyt'hichV are connectedito the ,heater element .l .356 of the .thermal delay switch 146Iand thecontact 352.

snaar/ss which in turn is connected upon closing of the switch 146 to the contact 354, lead 356 extending between contact 354 and the other side of the winding 342 and the lead 358 extending from the lead 356 and the other side of the winding 340 of the relay 136.

Solenoid windings 360 and 362 are energized from the low voltage transformer 150 through the lead 364 and branch leads 366 and 368 connecting to one side of windings 360 and 362, respectively; and upon the closing of contact 66 with respect to contact 58 through lead 70 extending from contact 58 to the Jones terminal C and lead 370 extending between the I ones plug terminal C through the normally closed contacts 372 and 374 of relay 136 and the lead connecting to the other side of the winding 360 which is in turn connected through lead 3'78 to the other side of the winding 362.

The switching solenoid winding 380 of the locking relay 144 is energized by the output of the tetrode 126 through the leads 382 and 384.

The secondary winding 281 of the lament transformer 148 is connected in parallel to the filaments of the tubes 126, 128 and 130 in conventional fashion from the leads 283 and 285.

In the circuit shown in FIG. 2 each of the tetrodes, 126, 128, and 130 comprises a time delay circuit. These circuits serve the purpose along with the thermal delay switch 146 to provide periods of time delay during various stages of each speed correction cycle. The timer comprising tube 128 is of rather short duration to serve the purpose of permitting small enlargements and depresses such as would result from bubbles, for example, to pass the sensing probe 20 without commanding the control circuit to correct the pulling speed of the puller assembly 12. The delay period for the timer tube 126, as will be described, is for the purpose of permitting actuating current to flow to the switches 92 and 100 during a stage of the correction cycle. This period is of rather short duration. The delay time of the timer tube 130 is of rather long duration and serves the purpose of permitting the extruder and puller 12 assemblies to effect proper corrections to the size of the tubing 14 in the presence of the slow response of the ilow of the material forming the tubing 14 and to permit the tubing to be moved from the extruder past the detecting point 22. In each of these circuits the cathodes 272, 252, and 236 set up an electron flow to the grids 386, 388 and 390 upon the closing of the on-off switch 158. The resultant current flow charges the `capacitors 392, 394 and 396 so that the points 398, 488 and 402 between the adjustable resistors 404, 406 and 408 and the current limiting resistors 410, 412 and 414 are negatively charged. Accordingly, when the normally open contacts of relay 138, for example, are closed by the energization of the winding 360 of the relay 138 current is conducted to the tetrodes but no current ow is present in the plate circuits of these tubes because the grids 386, 388 and 390 are held at cutoff by the negative bias imposed on the capacitors 392, 334 and 396 across the plate circuits. This negative bias is eventually dissipated by leakage through the resistors 404, 406 and 488 as determined by the time constant for the `adjusted value of the resistors 404, 406 and 408 and the capacitance of the associated capacitors 392, 394 and 396. After this negative bias has fallen to a suiciently low level the grids 386, 388 `and 390 are no longer at a cutoi potential and the contacts 262 andy 264 are closed. In these timinig circuits the capacitors 206, 208 and 210 are placed incircuit across the outputs of the tetrodes 126, 128 and 130, respectively, to eliminate chattering of the contacts of V- the locking relay 144 and the relay 132 operated by the outputs of tubes 126 and 128 and to avoid similar contact 6 chatter in the thermal delay switch 146 operated by the output of tube 130.

Having described the general circuit of the control system shown in FIGS. 1 and 2 the remaining details of the circuit included therein will be described in conjunction with the operation of the system. As previously stated this control system has two modes of operation. In one mode the circuits of FIGS. l and 2 effect a decrease in the pulling speed of the puller assembly 12 to cause the more slowly pulled tubing 14 to increase in diameter. In the other mode of operation the pulling speed of the puller assembly is increased to similarly effect a decrease in diameter of the tubing 14. In the embodiment of the control system described the contacts 58 and 60 are separately engaged by the contact 66 upon a change of .003 inch in the diameter of the tubing from a desired size and the pairs of contacts 54, 56 and 62, 64 are closed when the diameter of the tubing changes i008 inch.

When the diameter of the tubing 14 decreases by an amount equal to or greater than .003 inch, movement of the feeler probe 2@ will cause closing of the contacts 66 and 60 of the switch 44. This will result in the potential of lead 326 connected to the secondary winding of the transformer 158 being applied to one side of the relay windings 314 and 316 of the relays 134 and 140 through leads 328, 68, 78, 330, 336 and 338. The other sides of these windings are connected to the other side of the secondary winding 318 by leads 320, 322 and 324. This will result in the closing of the normally open contacts 258, 256 of relay 134 and the contact pairs 292, 294 and 410, 412 of relay and the opening of the normally closed contacts 414 and 416 of relay 134.

The opening of contacts 414 and 416 opens the circuit of the green lamps 418 and 420 which serve to provide a. visual indication that the control system is not effecting correction to the puller assembly because the diameter of the tubing 14 is Within l .003 inch of its desired diameter. These green lamps are connected across the winding 318 of transformer by leads 422, normally closed contacts 414 and 416 of relay 134, lead 424, normally closed contacts 426 and 428 of relay 138, lead 430 which connects to one side of the filament of the lamp 418 and lead 436 which connects through the Jones plug terminals I and I and lead 432 connected to one side of the iilarnent of lamp 420. The other sides of these lamp laments are connected by leads 434, Jones plug terminals I and l", lead 436 and lead 364 to the other side of winding 318. Accordingly, when relays 134 and 138 are unenergized these lamps are lighted but when either of these relays are energized the lamp circuit is opened.

Similarly, the closing of contacts 410 and 412 of relay 140 energizes the white lamp 438 through closing of the circuit comprising lead 440 extending between lead 68 and one side of the lamp filament and lead 442 extending from the lamp filament through Jones plug terminals K and K', lead 444, contacts 410 and 412 of relay 140 and lead 446 connecting to lead 324. The purpose of the lamp 438 is to indicate that correction should be made by the control circuit.

Closure of the contacts 256 and 258 of the relay 134 provides power from lead 266 which is connected to lead 228 and leads 245 and 246 to the cathode 252 of the timer comprising tube 128. After the above described time delay period, the plate circuit of the tube 128 hecomes conductive which effects energization of the winding 308 of the relay 132 through leads 310 and 312. This causes the normally open contacts 262 and 264 to close which in turn causes the timer comprising tube 126 tobe energized through leads 448 and 266. At the same time current 'is conducted through lead 286, connected to lead 266, through the normally closed contacts 282 and 284 of the locking relay 144, lead 280, lead 288, closed contacts 292, 294 of relay 140, lead 290, Jones plug terminals G and G and lead 98 to the solenoid winding of switch 166. As `previously described the other side of disagree,

162 is operated to decrease'current flow through the field winding 113 of the drive motor of the puller assembly 12 `to thereby reduce the pulling speed to effect an increase in the diameter of the tubing14. The switch 1li@ will remain energized for the duration of the time delay of the timer comprising tube 126.

Visual indication of the operation of switch 1li@ is effected by the completion of the circuit energizing the red timing lamp 2'78 through lead 281i. This lamp will remain lighted as Vlong as switch 106 is energized.

Upon tube 126 becoming conductive, the plate circuit leads 382 and 384 will energize theswitching winding 38? ofthe locking relay 144. This will result in the opening f contacts 232 and 234 thereby de-energizing the switch 160. At the same time, the timer comprising tube 130 will be started by the application of voltage to the cathode 236 through leads 232'and 23@ and the now closed contacts 224 and 226 of the locking relay.

The adjustable resistance 468 of thevtimer tube 130 is set to effect a rather long time delay before firing of the Vtube to permit a sufficient length of the tubing 14 to be moved from the extrusion head past the detecting point 22 and to allow for the delay in response resulting from the ow characteristics of the material forming the tubing. This will provide suihcient time so that the reduction inthe speed of the puller will haveits total elect on the diameter of the tubing.

When the tube 13d becomes conductive the plate circuit leads 34S and 346 energize the heating coil 3500i the thermal delay switch 146 4whose contacts352 and 354 close after suilicient heat is' developed to distortr a bie 'metallic element controlling the position of contact 352 in a conventional fashion. Upon the closing of switch'146,.

the output of timing tube 130 is applied through the lead 356 to the locking winding 342 of the locking relay 144. And, at the same time, the winding 346 of relay 136 is energized since it is in circuit with the winding 342.l

Accordingly the contacts 332 and 334 open thereby breakink7 theV energizing circuit, through lead 336, to deenergize the windings of relays 134 and 140. This results inthe turning oit ofthe entire control circuit even if'the correction yapplied to the puller assembly-is not enough .to break connection between contacts 66V and 66 of switch v44.

After -the eutireicontrol circuit has been turned oft` the thermal delay switch contacts will open after a brief cool- Wing period thereby'restoring the circuit ofthe winding 349 of relay 136'and the locking winding 342 of the locking relay 144m' its open circuit condition. This will restore the control circuit to its un-energized starting condition. itat this time contacts 66 and 6d remain closed, indicat ing more correction is required the above described cycle will be repeated and will be repeated as many times as necessary toincrease the diameter of the tubing 14 to within .063 inch of itsdesired diameter.

i' The operation of ythe control circuit insofar as thefunction of timer tubes'126, 12i5and 13d, locking relay 144 and relay 136 'is the'same when the Vdiameter ot thetubing 14 increases to .003 inchlor moreover the desired diame ter. The basic differencesl are that thetimer tube i128 is A started through the relay12l8 and control of yswitch 92 is eected through the Yrelay/142.l y

' When vthe contacts 66 and 580i theV switch v44 are closed by such increase in the diameter of tubing 14, the potentialv of contact 66 is applied to the Vwindings 361B and 362 of. the relays 138 'and 146 through Vlead 7i?, Jones plug Y terminals ).and C', lead 370, normally closed contacts' '372 and 374 of relay 136, lead 376 and lead 378. Upon energization of these windingsV 361i andr'362, normally closedcontacts 426 and 428 yof relay 13S will open and*Y causes the green lamps 418 and 429m be; turned olf by n disrupting the` supply Acircuit: lead 43?` energizing these lamps.

The red lamp 464 which provides visual indication that the diameter-.of tubing-14n enlarged by an amount greater than .003 inch is energized upon the closing of contactsl G land 392 of the relay 142. This is effected by breaking ,theV energizing circuit of this lamp which comprises Vleads 320,324, 446 and 466, contacts 390 and 302, lead 468, I ones plug terminalsL' and L, lead 47d, the filament of lamp 464leads 472 and 474, Jones plug terminals B vand'B'; and leads 476 and *3267.-l

ln this mode of operation 4of the control circuit, the cathode 252 of the timer tube 128.,r is energized by the closure of contacts 242 and y243 of the relay 138 and the circuit comprising leads 228, `240, 244,246 and 248.

After timer'tube 128 has been thu-s turnedon the operation of the circuit is the same until timer tube 126 is energized upon the closingof contacts 262 and 264 of relay 132. When this occurs vthe control switch 92 becomes energized through leads 286, contacts282 and 284 of the locking relay 144, leads 23d and 478, Vcontacts 460 Yand 462 of relay 142, lead 298, Jones plug terminals E and E, lead 88, the winding of switch 92, Ylead 90, Jones plug terminals F and F., and leads 306 and 394.

At the Sametime tube 126 is energized and switch 92 is closed the timing Vlamp 27S will be energized by the connection comprising lead 28,() to the filament of lamp 273. This, as in the previouslydescribedmodeof operation, provides visual indication 'that a-correction of speed ofthe puller' assembly 12 is being' made.

When timing tube 126 fires afterjits delay peri'odhas elapsed the switching windin'gtloi the-locking relay 144 is energized in the same manner as in the previous mode of operation. `Upon closing of the contacts 224 and 226 of this relay the cathode 2360i timer tube 139 becomes energized. After the delay period of tube`13tl thetherrnal delay switchV 146 isenergized'and upon closing of this switch the locking winding 342 of the locking relay 1,44

and the winding 340 of relay/'1136 are energized. The

results of, energizing these relays is the same except that the energization ofrelays 138 and 142 is'disrupted by the opening of switching contacts'372`and 374 of relay 136.V

Aspin the previously'described mode of. operation this cycle is repeated until the diameter of the tubing hasbeen suciently reduced to open contacts 66 and 53. of the probe kactuated switch 44. A Y

In each of the modes of operation describedV the indi- Y catorlamp 22d islighted upon the energizationot the i 220, 278, 41S, 438, 420 and 464, an indicator lamp 480 isproyided to indicate when the diameter of the tubing 14 is exceeding .0()8 1nch,;either as an increase or decreaserin diameter; The purpose of this indication is Vto: appraise the operator that the condition Vcausing the increase or decrease ofy diameter is not `being corrected Vrapidly enough vby` thercontrolsystem.Y Irrsuchy a case, the: operator Vwill speed up the correctionby manually,operatingV Y the switches 1d@ or 92by means of conventional switch `changes ofthe diameter ofthe tubing.

operatingV buttons V482 and Y484 V.until Y sufficient correction has been effected so that any furtherechanges inthe diameter of. thetubing can Vbe takencarezof by fthei'contr'ol system. Thisv usually occurs at the start'of operation of the-extruder 11li or when a diierent materialis used to make the tubing. Once suchmanual'fadjustment ismade the control system is capable'offtalring care of any-further are-tyres Such indication is provided by lamp 480 whose filament is connected directly to power line 164 by lead 486 and to power line 166 by lead 488 which is connected through contacts 490 and 492 of relay 494 or contacts 496 and 498 of a relay 500 and lead 502. In order to make this indicator salient a conventional flasher uni-t 504 is interposed in the leads 486 and 488. The relays 494 and 500 are actuated by means comprising the windings 506 and 508, respectively. The winding 506 is energized by lead 74, winding 506, lead 512 and lead 470 one side of the secondary winding 318 of transformer 150; and leads 72 and 474 to the other side of winding 318. The Winding 508 is similarly energized through leads 80 and 82 to one side of winding 318 of transformer 150 and lead 82, Winding 508 and lead 520 and 442 to the other side of winding 318. By virtue of this arrangement whenever the probe moves sufficiently upward as viewed in FIG. 1 contacts 54 and 56 will close or when the probe moves suiciently downward contacts 62 and 64 will close to energize the lamp 480.

From the foregoing it is apparent that the present invention provides an automatically operated control system which is responsive to a dimension of a continuously eX- truded article to maintain the dimension within an extremely close tolerance range. The use of this control system enables extrusion processes to be conducted at extremely high speeds with such speeds being limited only by the flow and setting characteristic of the material used in the process. Another important contribution to the art afforded by this control system is the elimination of waste sections of extruded articles which heretofore were simply cut out from the length of the extruded article.

It will be realized by those skilled in the art to which the invention pertains that by ordinary skills a variety of differently appearing control systems may be designed and constructed utilizing the features of the invention as embodied in the above described example of the control system of this invention. Accordingly, since the circuits and structures of this invention are susceptible to such modification the invention is to be considered as' being limited only by the appended claims.

I claim:

1. A control system which comprises:

an extrusion head for forming a continuous article;

pulling means for applying a continuous pulling force on said article in a direction away from said extrusion head whereby the magnitude of said force is proportioned to and determines a dimension of said article;

adjustable means for regulating the magnitude of said force;

sensing means responsive to said dimension of said article to effect an electric signal when said dimension deviates from a specified range of magnitudes; control circuit means responsive to said signal in circuit connection between said sensing means and said adjustable means responsive to said signal to provide an output to adjust said adjustable means, said control circuit means comprising a first time delay means actuated in response to said signal and a second time delay means actuated by the output of said first time delay means, said output of said first time delay means being connected to means to adjust said adjustable means so that no adjustment is'made during said first time delay to permit short time deviations to pass without adjustment, and wherein the output of said second time delay means is operable to dis'- connect the output of said first time delay means from said means to adjust said adjustable means so that said adjustment of said adjustable means is made during the entire second time delay period. 2. A control system as defined in claim l wherein: said control circuit further includes a third time delay means actuated by said output of said second time delay means, and wherein the output of said third time delay means is operable to disable said first and second time delay means.

3. A control system as defined in claim 2 wherein:

said sensing means is responsive to an increase in said dimension to effect a first signal and responsive to a decrease in said dimension to develop a second signal;

means responsive to said first signal to actuate said first timing means; and

means responsive to said second signal to actuate said first timing means.

4. A control system as defined in claim 3 wherein:

said first, second and third time delay means each comprise a tetrode.

5. A control system which comprises:

an extrusion head for extruding an article of continuou length; f

puller drive means for applying a pulling force on said article in a direction away from said extrusion head to control the dimensions of said article in accordance to the speed of said drive means;

adjustable means for changing the speed of` said drive means;

sensing means responsive to changes in said dimension to effect a first signal upon an increase in said dimensions and a second signal upon a decrease in said dimensions; and

control circuit means comprising a rst switch responsive to said first signal to actuate a first time delay circuit having an output after a first time delay period, said first time delay circuit being connected to prevent change in the speed of said drive means during said first time delay period to permit short changes in said dimension to pass without changing the speed of said drive means, a second switch responsive to said second signal to actuate said rst time delay circuit; the output of said first time delay circuit being connected to actuate a second time delay circuit having an output after a second time delay period and to actuate means for adjusting said adjustable means, the output of said second time delay means being connected to disable said means to adjust said adjustable means so that said adjustable means is adjusted during said entire second time delay period.

6. A control system as defined in claim 5 wherein:

said control circuit further comprises a third time delay circuit having an output after a third time delay period, said third time delay circuit being actuated by the output ofsaid second time delay circuit, said third time delay circuit being connected to prevent adjustment of said adjustable means during the third time delay period, and wherein the output of said third time delay circuit is effective to de-energize said first and second time delay circuits.

7. A control circuit las defined in claim 6 wherein:

said first, second and third time delay circuits each comprise a tetrode.

References Cited by the Examiner UNITED STATES PATENTS 1,867,225 7/32 Le Van et al 219-108 2,369,858 2/45 Ryan 18--13 2,372,162 3/45 Ryan 18-13 2,393,015 1/46 Bendz.

2,627,087 2/ 5 3 Hendry.

3,015,129 1/62 Hays et al 18-21 X WILLIAM J. STEPHENSON, Primary Examiner'.

MICHAEL V. BRINDISI, Examiner. 

1. A CONTROL SYSTEM WHICH COMPRISES: AN EXTRUSION HEAD FOR FORMING A CONTINUOUS ARTICLE; PULLING MEANS FOR APPLYING A CONTINUOUS PULLING FORCE ON SAID ARTICLE IN A DIRECTION AWAY FROM SAID EXTRUSION HEAD WHEREBY THE MAGNITUDE OF SAID FORCE IN PROPORTIONED TO AND DETERMINES A DIMENSION OF SAID ARTICLE; ADJUSTABLE MEANS TO REGULATING THE MAGNITUDE OF SAID FORCE; SENSING MEANS RESPONSIVE TO SAID DIMENSION OF SAID ARTICLE TO EFFECT AN ELECTRIC SIGNAL WHEN SAID DIMENSION DEVIATES FROM A SPECIFIED RANGE OF MAGNITUDES; CONTROL CIRCUIT MEANS RESPONSIVE TO SAID SIGNAL IN CIRCUIT CONNECTION BETWEEN SAID SENSING MEANS AND SAID ADJUSTABLE MEANS RESPONSIVE TO SAID SIGNAL TO PROVIDE AN OUTPUT TO ADJUST SAID ADJUSTABLE MEANS, SAID CONTROL CIRCUIT MEANS COMPRISING A FIS TIME DELAY MEANS ACTUATED IN RESPONSIVE TO SAID SIGNAL AND A SECOND TIME DELAY MEANS ACTUATED BY THE OUTPUT OF SAID FIRST TIME DELAY MEANS, SAID OUTPUT OF SAID FIRST TIME DELAY MEANS BEING CONNECTED TO MEANS TO ADJUST SAID ADJUSTABLE MEANS SO THAT NO ADJUSTMENT IS MADE DURING SAID FIRST TIME DELAY TO PERMIT SHORT TIME DEVIATIONS TO PASS WITHOUT ADJUSTMENT, AND WHEREIN THE OUTPUT OF SAID SECOND TIME DELAY MEANS IS OPERABLE TO DISCONNECT THE OUTPUT OF SAID FIRST TIME DELAY MEANS FROM SAID MEANS TO ADJUST SAID ADJUSTABLE MEANS SO THAT SAID ADJUSTMENT OF SAID ADJUSTABLE MEANS IS MADE DURING THE ENTIRE SECOND TIME DELAY PERIOD. 